1. Field of the Invention
The present invention relates to an audio signal processing technology, and more particularly, to an improved method and apparatus for automatically compensating a sound volume without an additional key manipulation by a user.
2. Description of the Background Art
FIG. 1 is a block diagram illustrating a conventional audio signal processing apparatus for a television set. As shown therein, the apparatus includes a tuning unit 101 for selecting a channel required by a user from a plurality of channels in accordance with high frequency broadcasting signals received through an antenna ANT, a wave detecting unit 102 for receiving an output signal of the tuning unit 101 and restoring a video signal and an audio signal, an input signal selecting unit 103 for outputting to an image processing unit the video signal received from the wave detecting unit 102 and outputting one selected from the audio signal outputted from the wave detecting unit 102 and an external audio signal EAUin, a voice control unit 104 for adjusting a sound volume of the audio signal AU output from the input signal selection unit 103 and outputting a resultant signal to a speaker SP, and a microcomputer 105 for controlling respective blocks in accordance with a user selected signal received from a key input unit 106.
The operation of the conventional audio signal processing apparatus will now be described.
First, in case a user intends to watch an areal wave broadcasting, when a required broadcasting channel is input through the key input unit 106, the input signal is applied to the microcomputer 105 which in turn outputs the corresponding control signal to the tuning unit 101.
The tuning unit 101 selects one of a plurality of channels with high frequency broadcasting signals through the antenna ANT, that is, the channel which corresponds to the control signal applied thereto from the microcomputer 105 selected by the user, amplifies the television broadcasting signal of the corresponding channel to a predetermined level, and outputs the amplified signal. Then, the wave detecting unit 102 restores an original video signal and an audio signal from the signal outputted from the tuning unit 101.
The input signal selecting unit 103 transfers the video signal among those outputted from the wave detecting unit 102 to the image processing unit, and the audio signal AU is transferred to the voice control unit 104.
When there is required a playback of an external device through an additional connection line other than the case in which an aerial wave broadcasting is watched, that is, when peripheral devices such as a VCR, CD(compact disc) player, and LD(laser disc) player, are connected to the television set for their playback, a user may carry out the key operation of a corresponding function through the key input unit 106, and the microcomputer 105 recognizes the key operation to thereby apply a control signal CS1 corresponding thereto to the input signal selecting unit 103.
Then, the input signal selection unit 103 selects one from the audio signal or external audio signal EAUin outputted from the wave detecting unit 102 in accordance with the control signal CS1, and outputs the video signal and audio signal to the image processing unit and the voice control unit 104, respectively. The voice control unit 104 receives the audio signal AU outputted from the input signal selecting unit 103, and adjusts the received signal to a volume level required by the user, that is, a volume level in correspondence to the control signal CS2 outputted from the microcomputer 105 so as to be applied to the speaker SP.
As described above, the conventional audio signal processing apparatus has a disadvantage in that a sound volume must be manually adjusted whenever a channel or an input audio source is changed if a user requires a certain level of audio output.
For example, a music signal and a voice signal show differences in frequency characteristic. Music allows an even distribution of frequency so that the music signal may sound larger than real in a human auditory system, whereas voice sounds weaker than music since human voice ranges from 1xcx9c5kHz.
Also, in many instances, a volume level tends to be unevenly outputted due to transmission level differences depending on broadcasting stations, receipt sensibility differences depending on districts, and record level differences of recording media, whereby the sound volume has to be manually adjusted by the user.
The present invention is directed to solution of the conventional disadvantages. Accordingly, it is an object of the present invention to provide a method and apparatus for automatically compensating sound volume, wherein a volume compensation is carried out according to an auditory frequency characteristic of human in consideration of a loudness curve, and a voice energy is calculated with regard to a half signal of a symmetrical audio signal so as to be converted to a simplified measurement.
To achieve the above described object, there is provided a method for automatically compensating a sound volume according to the present invention which includes a first step for determining whether a channel conversion key and an audio input switching key are inputted, a second step for producing an energy of an audio signal when the channel conversion key is inputted, and a third step for comparing an energy value of the audio signal detected for a predetermined time period with an energy value obtained from a previous step thereof and compensating for as much volume as a difference obtained by the comparison, thereby maintaining an absolute volume level.
Also, to achieve the above described object, there is provided a method for automatically compensating a sound volume according to the present invention which includes an input determination step for confirming whether an input mode of an audio signal is modified or a channel is modified, an energy production step for calculating an energy value of the input audio signal by predetermined cycles, and obtaining an average energy of the calculated energy value and an energy value obtained at a previous step thereof, an audio mode determination step for separating the input audio signal to an voiced interval and a voiceless interval, and determining whether the input audio signal is in a music mode or in a voice mode on the ground of the separated intervals, and a mode volume compensation step for calculating a compensated amount of the audio signal in consideration of an energy value produced in the energy production step and the audio mode, and carrying out a volume compensation in accordance with the collocated value.
Further, to achieve the above described object, there is provided an apparatus for automatically compensating a sound volume in a sound playback device which plays back sound with a provision of an external audio signal or an aerial audio signal according to the present invention, which includes a low-pass filter and amplifier for removing high frequency noise elements included in an input audio signal and amplifying the resultant signal to a predetermined level, an energy detecting unit for calculating an energy of the audio signal amplified in the low-pass filter and amplifier, a microcomputer for adding up an energy value of the audio signal obtained by the energy detecting unit for a predetermined time period, comparing the audio signal energy value with one obtained at a previous step thereof, and outputting a volume-compensated control signal corresponding to the compared resultant value, and a volume control unit for compensating an amplification rate of the input audio signal in accordance with the volume-compensated control signal.
Still further, to achieve the above described object, there is provided an apparatus for automatically compensating a sound volume in an audio device which amplifies and outputs a sound volume of an input audio signal in accordance with a user""s requirement according to the present invention which includes a switching unit for transferring an input audio signal to an A/D converter when the input audio signal mode is converted or a broadcasting channel is switched, an energy detecting unit for receiving a digital audio signal outputted from the AID converter, and obtaining and accumulating therein an energy value of respective intervals by predetermined cycles, an audio mode determining unit for comparing energy values of the obtained respective intervals with a reference energy value, counting in accumulation the intervals determined as voiced and unvoiced in accordance with the compared resultant value, and determining an input audio signal mode on the ground of the accumulated count value, a compensated amount calculating unit for obtaining an entire energy of the input audio signal on the ground the number of the voiced intervals counted during the predetermined frame period, obtaining a difference of the obtained entire energy and the reference energy value, and calculating a volume-compensated value in accordance with the difference value and the determined audio mode, and a digital signal processing unit including amplifier for amplifying a volume of the audio signal outputted from the A/D converter by use of the volume-compensated value.
The object and advantages of the present invention will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific example, while indicating a preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.